BLACKCAP (Sylvia atricapilla)
Fauvette à tête noire
The Blackcap is a pretty common bird in the woodlands, forests and scrublands of Switzerland - much more common than the Garden Warbler with which the song is easily confused. Most birds are summer visitors but a small number of individuals do overwinter here. It is found up to the tree line, but like the Garden Warbler is more common in lower areas below 800m. It too is a shy bird skulking in dense vegetation, but generally more visible than the Garden Warbler, or maybe I just see more of them because they are more common.
As explained under Garden Warbler these two can be really difficult to tell apart by song (visually of course the coloured head of the Blackcap is a clear feature). To me the Blackcap song is more deliberate in delivery than a Garden Warbler and less hurried, it also has harsher scratchier notes, whereas a Garden Warbler is more mellow:
Another feature of the Blackcap is that the last few notes of each phrase tend to fall into a rhythmic pattern, North and Sims (1958) describe this as "day-of-duty, duty-day" said quickly, I have kept it in my head and whilst not always matching that exact pattern I can recognise something similar in the final notes of most of the phrases of a Blackcap, try this one:
Here is a sonogram where those tail-end rhythm notes can be seen:
But its really not easy, try listening to these two together - Blackcap first with two phrases then Garden Warbler with two:
and finally here is the sonogram of that last comparison:
Side by side you can see a few more differences, the Blackcap song has many vertical lines indicating very brief notes covering a wide range of frequencies, especially in the second phrase, it is these sounds which give the song that rather "scratchy" feel. Also the Blackcap notes are mostly around 3.5 Khz whereas the Garden Warbler tend to be lower around 2.5 Khz, this gives the Garden Warbler song a slightly more mellow, Blackbird-type of feel to it.
Finally the alarm call of the Blackcap is quite distinctive, a sharp "chak !" like two stones being knocked together - similar to a Stonechat call; one day I was carefully recording a Turtle Dove when a Blackcap took exception to my presence and sat in front of the microphone and cursed me: